Fast and versatile electrostatic disc microprinting for piezoelectric elements

Nanoparticles, films, and patterns are three critical piezoelectric elements with widespread applications in sensing, actuations, catalysis and energy harvesting. High productivity and large-area fabrication of these functional elements is still a significant challenge, let alone the control of their structures and feature sizes on various substrates. Here, we report a fast and versatile electrostatic disc microprinting, enabled by triggering the instability of liquid-air interface of inks. The printing process allows for fabricating lead zirconate titanate free-standing nanoparticles, films, and micro-patterns. The as-fabricated lead zirconate titanate films exhibit a high piezoelectric strain constant of 560 pm V−1, one to two times higher than the state-of-the-art. The multiplexed tip jetting mode and the large layer-by-layer depositing area can translate into depositing speeds up to 109 μm3 s−1, one order of magnitude faster than current techniques. Printing diversified functional materials, ranging from suspensions of dielectric ceramic and metal nanoparticles, to insulating polymers, to solutions of biological molecules, demonstrates the great potential of the electrostatic disc microprinting in electronics, biotechnology and beyond.


1
Thank you for your review and constructive comments on the manuscript (NCOMMS-23-

19123-T) entitled "Ultrafast and Versatile Electrostatic Disc Microprinting for Piezoelectric
Elements" submitted for publication on Nature Communications. We have revised the manuscript carefully. All changes in the revised manuscript text file have been marked with red color. Please find responses to reviewers' comments below. 2

Reviewer #1 (Remarks to the Author):
The authors present here electrostatic disc microprinting (EDP), a scalable microprinting strategy capable of producing a variety of piezoelectric particles, films and patterns. The electrostatic forces used by EDP in an air-liquid interface allow for deposition speeds of to 10 9 micron^3/s^-1, which is one order of magnitude faster than comparable techniques.
Additionally, the electric field applied during EDP leads to a field-induced lattice deformation that allows fabricated PZT films to exhibit piezoelectric performances greater than other comparable fabrication methods. Using masks, in a photolithographic fashion, the authors also created piezoelectric film patterns with microscale resolution. Finally, using a judicious and fine control of the fabrication parameters of the EDP process, the authors demonstrated the creation of nanoparticles with good monodisperisity. The work presented here is not only original, but truly scalable, having the potential to transform current approaches to fabricate piezoelectric materials for wearable devices and IoT systems. The manuscript is nicely written and illustrated and the claims are mostly supported by the results. However, there are a few experimental details that remain obscure to the reader and I recommend the authors to address the following comments: 1-Line 63-64: "Such electrostatically driven cone-jetting phenomena occur widely in nature and application." This sentence is too vague (no application is mentioned until later) and reads weird. Please merge this sentence with the following one and re-write both, so that its split reads well.

Response:
We thank the referee for the careful review and professional comments. We have corrected the sentences in the revised manuscript on line 48-51, "Such electrostatically driven cone-jetting phenomena occur widely in nature and application, and two well-known examples are the ejection of streams of charged droplets from the tips of raindrops in a thunderstorm cloud and one immensely popular application for assaying large biomolecules: electrospray mass spectrometry." 2-Video 2: Please add some other labels indicating how the piezoelectric material is compressed. The video, otherwise, does not provide much information. 3

Response:
We thank the referee for the careful review and professional comments. 12 LEDs are lit up by our HIPCT device through palm tapping. We have corrected the Video S2 in the revised manuscript as suggested.
3- Figure 1a: This schematic should explain that the voltage applied to the tip is a positive voltage. It is, therefore, confusing why there are negative charges on the tip. The average tipsubstrate distance used during the experiments should be mentioned.

Response:
We thank the referee for the careful review and professional comments. The average disc-substrate distance used for depositing PZT films/patterns and nanoparticles is ~5 mm and ~60 mm, respectively. We have added the description in the revised manuscript on line 111-112, "The average disc-substrate distance is ~5 mm, and the other optimized process parameters are listed in Table S2." and line 199-200, "The optimized parameters for one-step depositing PZT nanoparticles are listed in Table S4."  4-The design of the "spiny disc" is not properly explained across the manuscript. What is the 5 maximum radius of this disc? Is there any limitation in terms of the number of outlets? Would it be benefitial for this disc to spin? Note that the authors called "spiny" but it doesn't spin! Please discuss all these issues in the manuscript, as they are critical to fully understand the fabrication method.

Response:
We thank the referee for the careful review and professional comments. The dimensions of the thin spiny disc used in our work is shown in Fig. S1a. Its diameter of addendum circle and dedendum circle is 5.5 mm and 5 mm, respectively. The topology of the multi-tips design helps trigger liquid-air interface instability at the rim of the disc, which is critical to generating multiple radial liquid ligaments.
By applying positive potential to different wetted spiny discs (spiny disc design in Fig.S1), multiple liquid jets are issued from the tips of disc, forming a symmetric radial jet mode ( Fig.   S2 and Fig. S3). As the increase of the disc diameter (D, from 3.5 mm to 10.5 mm), the applied voltage for generating stable cone-jets raise. For the small discs (D=3.5 mm), the ink is easy to flow out of the disc and drop onto the substrate, which inevitably will disrupt the uniformity of the deposited film. The liquid jet undergo Rayleigh-Plateau instability and will be split into droplet clusters with a diameter twice that of the jet. The amount of atomized droplets can be fine-tuned by controlling the number of tips (N). We find a well-defined optimum in atomization stability and productivity around N=16. At small N, atomizing yield is inhibited by the decreasing role of tip streaming; at high N, the mutual interference of jets/droplets is stronger, which affects the stability of jets.
In the rotation process of the disc, the centrifugal forces combined with the electric field force can elongate the liquid jet, which reduces the dependence on applied voltage and helps to increase the productivity. However, for our printing head, fluid stability on the disc is the primary issue to be addressed for the centrifugal assisted EDP.
We have added the description in the revised Supplementary Information (Supplementary Text Note S1 Formation of multiple jets) on line 60-73, "The dimensions of the thin spiny disc used in our work is shown in Fig. S1a. Its diameter of addendum circle and dedendum circle is 5.5 mm and 5 mm, respectively. The topology of the multi-tips design helps trigger liquid-air interface instability at the rim of the disc, which is critical to generating multiple radial liquid ligaments.
By applying positive potential to different wetted spiny discs (spiny disc design in Fig.S1), multiple liquid jets are issued from the tips of disc, forming a symmetric radial jet mode ( Fig.   6 S2 and Fig. S3). As the increase of the diameter of disc (D, from 3.5 mm to 10.5 mm), the applied voltage for generating stable cone-jets raise. For the small discs (D=3.5 mm), the ink is easy to flow out of the disc and drop onto the substrate, which inevitably will disrupt the uniformity of the deposited film. The liquid jet undergo Rayleigh-Plateau instability and will be split into droplet clusters with a diameter twice that of the jet. The amount of atomized droplets can be fine-tuned by controlling the number of tips (N). We find a well-defined optimum in atomization stability and productivity around N=16. At small N, atomizing yield is inhibited by the decreasing role of tip streaming; at high N, the mutual interference of jets/droplets is stronger, which affects the stability of jets. "  5-It is unclear if the piezoelectric material can be easily transferred (without losing its outstanding piezoelectric performance) from a conductive layer (necessary for its fabrication) to another substrate (non-conductive, for example). This should be discussed in the manuscript.

Response:
We thank the referee for the careful review and professional comments. The piezoelectric films and patterns are directly deposited onto the alumina substrates and polyethylene terephthalate (PET) substrates (or other non-conductive substrates). The sediment thickness (within 100 μm) and area (within 5 × 5 cm) are far smaller than the depositing distance (> 2 mm) and the area of electrically-ground stage (with a diameter of 20 cm), respectively. Therefore, the substrates and dielectric masks have very limited effect on the electric field between disc and ground electrode. The stable atomizing state is maintained throughout the entire deposition process.
The PZT patterns deposited on the PET substrates shown in this work (Fig.3c, e and Fig. S9) are only dried at 200 ℃ for 2 min. EDP-derived piezoelectric films will be crystallized at low temperature by laser assisted annealing in our future work. We have added the description in the revised manuscript on line 178-183, "The patterns are directly deposited onto the polyethylene terephthalate (PET) substrates. The sediment thickness (within 100 μm) and area (within 5 × 5 cm) are far smaller than the depositing distance (> 2 mm) and the area of 8 electrically-ground stage (with a diameter of 20 cm), respectively. Therefore, the substrates and dielectric masks have very limited effect on the electric field between disc and ground electrode. The stable atomizing state is maintained throughout the entire deposition process.
The PZT patterns deposited on the PET substrates are only dried at 200 ℃ for 2 min." 6-(In line with the previous comment). It is also unclear how the mask used to make micropatterns can be removed without removing the micropatterns too. The authors should explicitly mention this effect and explain that, due to the adhesion of PZT to the substrate, the minimum feature size was (insert-here-figure-of-merit).

Response:
We thank the referee for the careful review and professional comments. The micropatterns are fabricated by dielectric mask-assisted EDP. The substrates are covered with polyimide films with a thickness of 200 μm, which are then patterned by an electronic craft cutting/engraving tool (Silhouette Cameo 4). By keeping the substrate electrically-ground well, we electrostatically guide the nanodroplets towards the attractive area (holes of the mask), whilst being away from the repulsive area (dielectric film) (Fig. 3a). Because the attractive area is recessed relative to the repulsive area, charged particles accumulation around the edge of the holes (attractive areas) occurs and will prevent nanoparticles deposition near the edge of the attractive area. This funneling effect will reduce the width of the area coated with deposited nanoparticles, which can push the resolution of assembly beyond that of the defined dielectric mask. During evaporation of the solvent in the wet films, cracks appeared for the films deposited on the polyimide surface due to the sol induced shrinkage stresses. The mask can be easily removed after deposition without affecting the functionality of the patterns. (Fig. S10a).
The sloping side walls for deposited patterns are formed due to the funneling effect (Fig. S10b, c). Previously such features were attributed to edge fractures during masks removal. However, after examination of the similar cross sections with the masks, it can be seen that these sloping side walls still exist and are caused due to the funneling effect (particles located at the edge of the mask shielding the subsequent particles deposition) and the diffusion of wet films. Given the fact that the deposited inks remain wet for a few seconds after printing, the consequent diffusion of wet films occurs. We have added the description in the revised manuscript on line 152-161, "Charged nanoparticles and droplets, generated by EDP, are simultaneously deposited onto the substrates, which are covered by the dielectric mask (Fig. S8). By keeping the substrate electrically-ground well, we electrostatically guide the nanoparticles towards the attractive area (holes of the dielectric mask or target region), whilst being away from the 9 repulsive area (dielectric film or mask region) (Fig. 3a). Because the attractive area is recessed relative to the repulsive area, charged particles accumulation around the edge of each hole (mask region) occurs and will prevent nanoparticles deposition near the edge of the attractive area. This funneling effect will reduce the width of the area coated with deposited nanoparticles, which can push the resolution of assembly beyond that of the defined dielectric mask. The mask can be easily removed with tweezers following deposition and heat treatment without affecting the functionality of the patterns." and line 167-168, "The sloping side walls for deposited patterns are formed due to the funneling effect and the diffusion of wet films (Fig.   S10)." Some physical properties (including viscosity, surface tension, electrical conductivity, and relative permittivity and) of the PZT inks are measured and listed in Table S1. The viscosity of the PZT slurry is measured using an Ubbelohde viscometer. The surface tension is measured by a contact angle meter (Krüss DSA 100, Krüss GMBH). The relative permittivity is obtained by a precision impedance analyser (4294A, Agilent Technologies).The electrical conductivity is measured by a conductive meter (DDS-307, Shanghai INESA Scientific Instrument). The material properties suitable for obtaining a stable cone-jet mode used in electrohydrodynamic tip streaming process require an electrical conductivity of more than 10 -11 S m -1 , a surface 11 tension of less than 50 mN m -1 and a viscosity of less than 100 mPa s -1 [4]. It can be seen from Table S1 that our PZT inks meet the requirements for obtaining a stable cone-jet mode. We have added these descriptions in Table S1 of the revised supplementary information on line 345-354.
The collision and dispersion of droplets on the substrate play an important role in the evolution of the as-deposited structures. For the high-concentration inks, atomized solvent-depleted particles tend to form a 'powdery' deposit and be exceedingly agglomerated owing to their poor mobility. These resident particle clusters will attract subsequent particles to agglomerate to them under the electrical field, referring to preferential landing. For the low-concentration inks, atomized particles enveloped by sol can improve the flow activity of the deposited wet films, which will increase the bonding behavior of the particles and reduce the porosity of films.

Reviewer #2 (Remarks to the Author):
In this manuscript, the authors developed ultrafast and versatile electrostatic disk microprinting (EDP) for piezoelectric elements. The EDP process could fabricate lead zirconate titanate (PZT) free-standing particles, films, and micro-patterns at a high speed of 10 9 μm 3 /s. The fabricated PZT films showed a high piezoelectric strain constant of 590 pm/V, which is 1~2 times higher than previous research. In general, the experiment is well designed, and the conclusion is logically supported by the experimental results. However, there are still some issues to be addressed. It needs revisions and improvements for acceptance. Comments: 1. The authors proposed electrostatic disc microprinting (EDP) with the spiny disc. However, spiny disc contained 16 outlets at the end tip of nozzle, and thereby, entire spiny disc could be considered a type of multi-nozzle that has shape of disc. Therefore, a word 'nozzle-free' should be removed or replaced to another word. Also, some articles are recommended when introduced the electrostatic printing technique with multiple nozzle or nozzle-free to improve large-scale production: 10.1016/j.jiec.2015.06.033; 10.1021/acsaem.7b00227.

Response:
We thank the referee for the careful review and professional comments.

Response:
We thank the referee for the careful review and professional comments. "five tips" has been corrected to "six tips".
By applying positive potential to different wetted spiny discs (spiny disc design in Fig.S1), multiple liquid jets are issued from the tips of disc, forming a symmetric radial jet mode (Fig.   S2). As the increase of the disc diameter (D, from 3.5 mm to 10.5 mm), the applied voltage for generating stable cone-jets raise. For the small discs (D=3.5 mm), the ink is easy to flow out of the disc and drop onto the substrate, which inevitably will disrupt the uniformity of the deposited film. The liquid jet undergo Rayleigh-Plateau instability and will be split into droplet clusters with a diameter twice that of the jet. The amount of atomized droplets can be finetuned by controlling the number of tips (N). We find a well-defined optimum in atomization stability and productivity around N=16. At small N, atomizing yield is inhibited by the decreasing role of tip streaming; at high N, the mutual interference of jets/droplets is stronger, which affects the stability of jets. The simplification of electrical simulation with six tips of the spiny disc can avoid mutual interference of jets, even though it causes a decrease in droplets depositing ratio. We have added the description in the revised Supplementary Information (Supplementary Text Note S1 Formation of multiple jets) on line 60-73, "The dimensions of the thin spiny disc used in our work is shown in Fig. S1a. Its diameter of addendum circle and dedendum circle is 5.5 mm and 5 mm, respectively. The topology of the multi-tips design helps trigger liquid-air interface instability at the rim of the disc, which is critical to generating multiple radial liquid ligaments.
By applying positive potential to different wetted spiny discs (spiny disc design in Fig.S1), multiple liquid jets are issued from the tips of disc, forming a symmetric radial jet mode ( Fig.   S2 and Fig. S3). As the increase of the diameter of disc (D, from 3.5 mm to 10.5 mm), the applied voltage for generating stable cone-jets raise. For the small discs (D=3.5 mm), the ink is easy to flow out of the disc and drop onto the substrate, which inevitably will disrupt the uniformity of the deposited film. The liquid jet undergo Rayleigh-Plateau instability and will 15 be split into droplet clusters with a diameter twice that of the jet. The amount of atomized droplets can be fine-tuned by controlling the number of tips (N). We find a well-defined optimum in atomization stability and productivity around N=16. At small N, atomizing yield is inhibited by the decreasing role of tip streaming; at high N, the mutual interference of jets/droplets is stronger, which affects the stability of jets. " The demand for 3D conformal fabrication is increasingly growing, driven by the potential of integrating functional materials on a curvilinear surface for fundamentally new characteristic.
As one solution chemistry design-derived deposition, our EDP process has strengths in massive production. For large-area thin films or micropatterns, EDP is more suitable than spin or dip coating since there are no limitations on the size or geometry of the substrate. Note that 3D substrates with complex geometries should preferably be electroconductive for massive production. Given the fact that the deposited inks remain wet for a few seconds after printing, the consequent diffusion of wet films occurs. So the deposited material is easily to spread to the recessed region of the substrates and achieve completely covering of the 3D electroconductive surface. Here, we use EDP to conformally and uniformly deposit PZT films and patterns on the 3D free-form stainless steel substrates, cloth substrates and wrinkled steel sheet ( Fig. 3e and Fig. S7). High-precision conformal printing of films and patterns should using a moving stage with the capability of robotic control of substrates and complex printing algorithms. We have added the description in the revised manuscript on line 120-129, "The demand for 3D conformal fabrication is increasingly growing, driven by the potential of integrating functional materials on a curvilinear surface for fundamentally new characteristic 37,38 . Considering that the height step of each deposited layer (< 4 μm) is relatively small compared to the depositing distance, the effect of the reverse charging from as-deposited products to electric field is too small to disturb the precise layer-by-layer assembly. The deposited inks remain wet for a few seconds after printing, so the sediment will tend to spread to the recessed region of the substrates, which contribute to achieve 3D conformal printing. We use EDP to conformally and uniformly deposit PZT films on the 3D free-form stainless steel substrates, cloth substrates and wrinkled steel sheets (Fig. S7), demonstrating promising potential in 3D conformal electronics and smart textiles."    3. Ejected materials are highly charged and moved along the induced electric field. However, depending on the deposition range, speed, and tip-to-collector distance, the range of ejected materials may enlarge with being deposited on the undesired region or substrate. Can the undesirable deposition of as-deposited films or patterns be adjusted with just multiple prints using an X-Y mechanical stage and PZT sol spin-coating process?

Response:
We thank the referee for the careful review and professional comments. During the deposition of films and patterns, it is inevitable to enlarge the range of ejected droplets to undesired region for the uniformity of the films on the desired substrates. For example, to obtain a uniform film on a 20×20 mm substrate, the range of the ejected droplets (the moving range of the X-Y translational stage) is adjusted to 25×25 mm (Fig. S20).

Response:
We thank the referee for the careful review and professional comments. Given that the mask will be detached after the deposition and heat treatment, it is believed that a significant amount of unused deposited materials would be wasted. We calculated the coverage ratio of PZT on the target region and mask region by measuring the covered area of PZT based on ImageJ.
Using polyimide mask with ~200 μm-wide grooves, the coverage ratio of PZT on the target region and mask region is 92.5 ± 1.2 % and 21.6 ± 6.6 %, respectively. A sparse amount of PZT is deposited on the mask region due to the unstable jet and the electrostatic repulsion between the deposited and coming droplets. We have added the description in the revised manuscript on line 168-173, "Given that the mask will be detached after the deposition and heat treatment, it is believed that a significant amount of unused deposited materials would be wasted. For example, using polyimide mask with ~200 μm-wide grooves, the coverage ratio of PZT on the target region and mask region is 92.5 ± 1.2 % and 21.6 ± 6.6 %, respectively. A sparse amount of PZT is deposited on the mask region due to the unstable jet and the electrostatic repulsion between the deposited and coming droplets." and line 339-340, "We calculated the coverage ratio of PZT on the target region and mask region by measuring the covered area of PZT via ImageJ." 5. In the Abstract, the authors declared that the EDP process allows for one-step fabrication of PZT nanoparticles, films, and micro-patterns. However, spin-coating with PZT sol conducted to further improve the density of the as-deposited films. Without the spin-coating process, can PZT films and micro-patterns be fabricated well? If not, the word 'one-step' should be applied to fabricate only PZT nanoparticles in the whole manuscript or removed to avoid misunderstanding to readers.

Response:
We thank the referee for the careful review and professional comments. The purpose of spincoating with PZT sol is to further improve the density of the as-deposited films, and thus 20 improve their electrical properties. The calculation of depositing speed of EDP and the piezoresponse measurements of films are based on PZT films with sol spin-coating. In order to avoid misunderstanding to readers, the word 'one-step' has been removed in the whole manuscript.
6. In general, the performance of energy harvesters includes not only output voltage but also output current. However, in the paper, only the output voltage performance graph is showed.
Therefore, to show the device performance, the current graph according to variable, such as frequency and force, is recommended to be added.

Response:
We thank the referee for the careful review and professional comments. The output current of the HIPCT-based energy harvester as a function of the compressive pressure/resistance are measured, as shown in Fig. S15e, f. The output current increases gradually from ∼15 μA to 7. In general, the performance of a pressure sensor is verified by sensitivity, such as the amount of generated power (V/N or V/Pa) according to the pressure (force) and R-squared score.
However, in Figure S11, which shows the performance as the pressure sensor, it is difficult to know quantitatively the sensitivity of the device. Correspondingly, it is recommended to add the above two indicators for the quantitative inspection.

Response:
We thank the referee for the careful review and professional comments. The amount of generated power according to the pressure is 13.6 ± 0.5 V/MPa, and R-squared score is 0.978.
We have added these description in Fig. S15c.

Response:
We thank the referee for the careful review and professional comments. The description of

Response:
We thank the referee for the careful review and professional comments. Our EDP process can trigger structural distortions of PZT films (Table S5)   Besides, when discussing compatibility of common patterning techniques with flexible and stretchable substrates, the authors should mention PVDF and related co-polymers more explicitly in the state of the art, since these materials seem increasingly important in the relevant field.

Response:
We thank the referee for the careful review and professional comments. Poly(vinylidene fluoride) (PVDF) is a very promising material for fabricating flexible and wearable devices due to its ferroelectricity, piezoelectricity, flexibility as well as excellent. Micropatterning of PVDF films is an essential step in fabrication process in order for the sample to be integrated  18,19 or micromold-assisted process 20 (soft lithography). For inorganic piezoelectric ceramics, the above patterning techniques lack compatibility with flexible and stretchable substrates." On page 5 (line 209) the authors claim, that their technology facilitates the realization of "highquality" piezoelectric films. However, the label "high-quality" of thin films comprises more than a high piezoelectric coefficient, it is also concerned with things such as surface roughness, achievable layer uniformity and homogeneity, and the constraints with regard to substrate dimensions that arise as a consequence.

Response:
We thank the referee for the careful review and professional comments. This vague expression has been deleted, and we have added these descriptions in Results section of the revised manuscript on line 227-229, "EDP strategy and in-situ electrostatically crystallographic structure upgrading are capable of fabricating PZT films with the thickness up to 50 μm and effective piezoelectric coefficient of ~560 pm/V." Authors should also comment on issues like reproducibility (piezoelectric and structural properties) in fabrication, as well as on durability and aging effects of the fabricated PZT 27 structures. For example, a well-known problem of PZT is resistance degradation under electrical field load, additionally strongly dependent on the used electrode material. How do the layers fabricated by the proposed technology perform in this respect?

Response:
We thank the referee for the careful review and professional comments. As for all printing techniques, the process parameters should be optimized for the given ink and the reproducibility of the printed products is of principal importance. Here, the reproducibility and consistency of the EDP process is assessed by analyzing the piezoelectric and structural properties of PZT films/patterned lines that are printed via the optimized process parameters (Table S2). Three PZT films with the thickness of <10 μm are deposited at different times.
PFM is used for piezoresponse measurements using an Asylum Cypher ES AFM system with a conductive probe (Nano world Arrow-EFM). For calculating piezoelectric coefficient d33, an area (500 × 500 nm) was scanned in DART (dual AC resonance tracking) mode with varied tip drive voltage (from 10 mV to 200 mV), and the corresponding out-of-plane piezoelectric amplitudes are recorded over the scanned area. The maximum and minimum measured value is ~470 and ~648 pm/V, respectively. The mean value is ~560 pm/V. Three samples with PZT linear structures arrays are fabricated via polyimide mask with ~100 μm-wide grooves. The widths of printed lines for each printed sample are measured at ten different positions. There is no statistically significant difference among any of the widths measured at the same sample (Fig. S21). These data indicate that our EDP can fabricate PZT films and micropatterns in a consistently uniform manner. We have added these descriptions in the revised manuscript (Results Versatility and reproducibility of the EDP process) on line 273-287, "As for all printing techniques, the process parameters should be optimized for the given ink and the reproducibility of the printed products is of principal importance. Here, the reproducibility and consistency of the EDP process is assessed by analyzing the piezoelectric and structural properties of PZT films/patterned lines that are printed via the optimized process parameters (Table S2). Three PZT films with the thickness of <10 μm are deposited at different times.
PFM is used for piezoresponse measurements using an Asylum Cypher ES AFM system with a conductive probe (Nano world Arrow-EFM). For calculating piezoelectric coefficient d33, an area (500 × 500 nm) was scanned in DART (dual AC resonance tracking) mode with varied tip drive voltage (from 10 mV to 200 mV), and the corresponding out-of-plane piezoelectric amplitudes are recorded over the scanned area. The maximum and minimum measured value is ~470 and ~648 pm/V, respectively. The mean value is ~560 pm/V. Three samples with PZT linear structures arrays are fabricated via polyimide mask with ~100 μm-wide grooves. The widths of printed lines for each printed sample are measured at ten different positions. There 28 is no statistically significant difference among any of the widths measured at the same sample (Fig. S21). These data indicate that our EDP can fabricate PZT films and micropatterns in a consistently uniform manner." The effective piezoelectric coefficient value of PZT films has be corrected to '560 pm V -1 ' in the whole manuscript.
Normally, the long-time service process of the piezoelectric films is accompanied with the increase of the leakage current, eventually resulting in the breakdown. The above phenomenon is called as the electric degradation. Here, the leakage current measurements of our PZT films with Ag electrodes is conducted under a DC bias field of 150 kV/cm and a temperatures of 180 ℃. The applied electric field is directed from the top to the bottom electrode. Ag top electrodes with diameters of 1 mm are printed onto the PZT surface by EDP (Fig. S22a).
Measurements of current are made 60 s after any change in value to allow the current to stabilize.  Table S2. Optimized process parameters for EDP depositing PZT films/patterns.